A Click reaction is one that yields a product quantitatively or nearly so while being tolerant to a wide range of solvents, including water, and pH conditions and having a strong thermodynamic driving force. These characteristics are attractive when designing new approaches to building small molecules and materials. Reactions that have the characteristics of a Click reaction were originally pursued in the field of drug discovery, and the approach has led to an immense number of potential drug targets in a manner that is easier and less expensive than earlier synthetic approaches used for drug discovery.
Of the reactions that are classified as Click reactions, the most recognized and prolifically applied is the copper catalyzed azide-alkyne cycloaddition (CuAAC) to yield 1,4-disubstituted 1,2,3-triazoles, as shown in Scheme 1, below. This reaction is particularly accessible due to: the ease of synthesis of the alkyne and azide functional reactants in nearly quantitative yields; the tolerance of the reaction to a wide variety of solvents, including water; the regioselectivity of the reaction toward synthesis of 1,4-disubstituted triazoles; and the high tolerance of alkyne and azide functional groups to most other functional groups. CuAAC represents the qualities of a Click reaction so well that it is often referred to simply as “the click reaction”.

Despite the great activity of Click Chemistry and, particularly, CuAAC, there are few applications of these reactions in inorganic or organometallic chemistry. CuAAC has been applied to the functionalization metal clusters with organic moieties and to the synthesis of organic ligands to be employed with metal ions. Neither the CuAAC nor any Huisgen 1,3-dipolar cycloaddition reaction has not been explored to directly link two or more metal ions. Organobimetallic and multimetallic compounds employing the cycloaddition of metal-azides and metal-acetylides should be useful as bimetallic catalysts, polymers, and 2- or 3-dimensional covalent metal organic networks, including those where a plurality of identical or different metals are isolated and at least two metals are separated by a 1,2,3-triazole ring.